1. Field of the Invention
The present invention relates to an improved apparatus and method of molding a composite foam molding element having a top side member and a back side member integrated with each other via a foam member and a novel composite foam molding element obtained by the same.
2. Description of the Related Art
Conventionally, as a method of manufacturing a composite foam molding element having a top side member and a back side member integrated with each other via a foam member, there is adopted a method described in Japanese Patent Application Laid-open Nos. 4-344227 and 6-210753.
A general description of a molding apparatus used by this method will be given with reference to FIG. 8. First, a space 16 for molding a foam member is formed between a bottom face of an upper die 11 and a top face of a lower die 15. Then, the top face of the lower die 15 is formed of an air ventilation porous member 18. A skin 17 attached to the surface is pressure-reduced from a lower discharge space 19, whereby the skin can be adsorbed by and fixed to the top face of the lower die 15. In addition, the inside of the upper die 11 is divided into a left steam chamber 11a comprising a left steam pipe 11c and a right steam chamber 11b comprising a right steam pipe 11d. A ventilation hole 12a and a raw material bead supply pipe 13a are disposed at the bottom face of the left steam chamber 11a. Similarly, a ventilation hole 12b and a raw material bead supply pipe 13b are disposed at the lower face of the right steam chamber 11b. 
In a molding method using such apparatus, the skin 17 is disposed while the skin is adsorbed by a ventilation porous member 18. Next, base material 14 is disposed at the lower face of the upper die 11 to ensure the upper and lower dies are closed, and a space 16 for forming a foam member is provided. In this case, at the base material 14, there are provided through holes 14a 14d, 14a and 14b that correspond to the ventilation holes 12a and 12b and openings of the raw material bead supply pipe 13a and 13b, respectively. Here, raw material beads are charged in the space 16 through the raw material bead supply pipes 13a and 13b while charging air is supplied. In this case, however, the steam chambers 11a and 11b maintain pressure reduction without supplying a steam, and discharge the air in the space 16 through the ventilation holes 12a and 12b. In this way, the charging air supplied together with raw material beads is forcibly discharged, and only the raw material beads can be left and charged in the space 16.
However, in this molding apparatus, 12a and 12b are operated to pressure reduction at the same time. Thus, raw material beads are hardly charged at the periphery in the space 16. Moreover, in the case where the thickness of this space 16 is small, and an area is large, in particular, partial occlusion occurs during charging, and the raw material beads hardly reach a portion distant from the through holes 14a and 14b of the raw material bead supply pipes 13a and 13b. As a result, non-uniform charging unavoidably occurs.
In addition, as the molding method using this apparatus, there has been adopted a heating method in which heating steams are supplied sequentially from the left steam pipe 11c of the upper die 11 to the left steam chamber 11a, and then, to the steam hole 12a, and the charged raw material beads are heated, and then, is sequentially supplied from the ventilation hole 12b to the right steam chamber 11b, and then, to the right steam pipe 11d, and is discharged. However, in such heating method, there occurs a tendency that the flow of the heating steam in the space 16 short-passes between the closest ventilation holes 12a and 12b. Thus, in a case shown in FIG. 8, although fusion advances at the center portion, there occurs a deviation that fusion is delayed at a portion close to the right and left ends. As a result, there has been a serious problem that non-uniform quality in gravity, appearance, and strength of products occurs.
In addition, when a skin, base material, and a foam member are discussed from the aspect of material, for example, in a conventional combination used in a dashboard of an automobile, vinyl chloride, polypropylene, and urethane are used for the skin, back side member, and foam member, respectively, and the top and back materials are integrated in contact with each other. In recent years, there has been a growing need for causing each part of the skin, base material, and foam member to be formed of a material with the same components, making it possible to ensure recycling. From this point of view, technological development in which an olefin based elastomer (TPO) is extensively used for a skin, and an olefin based polypropylene foam (ERP) is extensively used for a foam member becomes an important task. The foregoing documents describe that a polypropylene based or polyethylene based sheet, a filler-containing solid resin, a foam resin bead or the like is used as an olefin based resin material for skin 17, base material 14, and foam member. However, with this method as well, it has been extremely difficult to uniformly manufacture a thin, composite foam molding element in different elongated shape having its comparatively small thickness, large area, and irregularities and curves, as is the case with a drain pan member of an air conditioner or a dashboard of an automobile, for example.
Further, in the conventional method, ventilation holes 12a and 12b for pressure reducing or steam supply are disposed with intervals of 25 mm to 50 mm, and correspondingly, through holes 14c and 14d are provided at the base material 14. Thus, there has been problems with higher die processing and assembling costs and lower strength of a composite foam molding element caused by the lowered strength of the base material 14.
Therefore, it is an object of the present invention to provide a molding apparatus and method for improving the uniformity of raw material beads charged in a cavity for molding a foam member in molding technique for integrating the top and back side members with each other via a foam member and molding these members, and improving the uniformity of heating and fusion of these charged raw material beads, the molding apparatus and method capable of manufacturing a thin, composite molding element in different elongated shape having its comparatively small thickness, large area, and irregularities and curves that has been hardly manufactured in the conventional techniques.